1. Field of the Invention
This invention relates to endoscopes which are widely used in the field of medicine and in particular to a compact endoscope having a fine diameter probe for use in hospitals and doctors"" offices for outpatient procedures.
2. Description of the Related Art
Currently, orthopaedic surgeons perform the greatest number of arthroscopic in-hospital procedures, approximately half of which could be performed on an outpatient basis. Almost 2.5 million such procedures are undertaken annually. Of these, 510,000 are for shoulder injuries, 1.7 million are for knee injuries, and 200,000 are for such procedures as elbows, ankles and wrists. The future arthroscopic market is expected to be additionally enhanced by anticipated developments in the fields of synthetic bone and tissue transplantation.
Currently available endoscopes have the disadvantages of being bulky, expensive instruments which are typically found only in hospitals. Available endoscopes have relatively large diameter optical probes, requiring proportionately large incisions to permit their use. There is a need in the art for a compact, small diameter endoscope, which may be purchased and used by medical professionals in their offices to perform outpatient diagnostic and surgical procedures.
There are at least two major technical obstacles to the design of an endoscope having an outside diameter of less than 2 mm. The first obstacle is that of insufficient illumination. An endoscope must both provide light to the area within the body being viewed and collect sufficient reflected light to be detected by available sensor arrays. The narrow optical pathways available in a very small diameter endoscope have typically not been capable of transmitting or collecting sufficient light.
The quantity of light transmitted in any optical arrangement is principally determined by two factors: 1) the optical characteristics of the light receiving surface of the arrangement (surface area, curvature, etc.); and 2) the intensity of the light energy incident upon that surface. Reduction in either factor reduces the amount of light transmitted.
In conventional endoscopic systems, these transmission constraints restrict the ability to effectively reduce the diameter of the probe which delivers light into the cavity to be viewed and collects the reflected image. Light sources of conventional brightness are not compatible with optical transmission systems which employ a significant reduction in the surface area of the light transmission pathway. Accordingly, there is a need in the art for an endoscopic system which can deliver sufficiently intense light energy to an endoscope to permit reduction in the light transmission portion of an endoscope probe.
Collection of the reflected light which will form an image of the viewing area presents another set of technical difficulties. Prior art endoscopes typically focus the image on either a charge coupled device (CCD) sensor array or magnify the image into an eye piece that the surgeon or medical professional can view directly. Ideally, a single glass rod could be used to transmit image light from an object lens to the sensor array. Such a construction is employed in many larger diameter conventional endoscopes. However, as the diameter of such a glass rod is reduced, the rod becomes vulnerable to stress induced birefringence, which distorts the image being transmitted.
Conventional optical fibers, while they are thin enough to be flexible and avoid the problem of birefringence, have cross sectional surface areas which individually collect only limited amounts of light. No matter how many such fibers are used, the brightness of the transmitted image is not enhanced because the optical characteristics of the receiving or input face of each fiber do not change. Thus, there is also a need in the art for a fine diameter endoscope probe which uses a single optical pathway to collect and deliver image light to a suitable sensor array.
Briefly stated, the invention in a preferred form comprises a compact, office-based fine diameter endoscope system which employs a pulsed xenon light source and novel image delivery optics to provide an endoscope probe having a diameter which is reduced in comparison to comparable conventional probes. The micro-endoscope system (ME system) includes a service module, a combined optical and electronic service cable and a micro-endoscopic device (MED). The service module houses the system power supply, the pulsed xenon light source, the image processor and the control electronics as well as the display/monitor. The combined optical and electronic cable contains a fiber optic bundle to transmit light from the service module to the MED and conductors to communicate with the electronic portion of the MED.
The MED comprises a sensor head that contains a sensitive charge coupled device (CCD) sensor array, a light pulse transfer interface and image focus optics. Controls allow the user to control the focus and magnification functions. A removable, one-piece optical probe and ergonomic grip slides over the sensor head to mate with the light pulse transfer interface. The optical probe includes a light pipe to deliver light from the pulse transfer interface to the viewing area and an image path for collecting and guiding reflected light back to the image focus optics. The pulse transfer interface enhances the transfer of light from the fiber optic bundle to the light pipe. Light travels the length of the light pipe and is directed upon the area to be viewed. Light reflected from the viewing area is collected by an object lens and focused into the image path. The image path guides reflected light to the image focus optics in the sensor head where the image is focused on the CCD array. Image data from the CCD array is communicated to the service module electronics through the service cable.
To enhance the intensity of light incident on the optical components of the light path, the MED utilizes a pulsed xenon light source which emits short duration, very high-energy pulses of light. Each pulse of light may be in the energy range of 100,000 watts and have a duration of approximately 10 microseconds. The pulsed xenon light source is essentially a point source of light. The pulsed xenon light source is positioned so the emitted pulses of light pass directly into the input end of the fiber optic bundle. The highly concentrated light energy provides sufficient illumination of the viewing area while employing a smaller diameter light path.
Image path optics having a diameter of approximately 1 mm address the issue of birefringence by using an image guide comprised of glass rod segments. Short rod segments are not prone to the stresses which induce birefringence. The sections of the image guide are assembled to form an integrated guide having the length desired for the optical probe. An alternate embodiment of the image guide may be constructed of optical grade plastic, such as polyethylene.
An object of the present invention is to provide a new and improved fine diameter endoscope having an efficient and cost effective construction and which is adaptable for use in out-patient clinics and doctors"" offices.
Another object of the present invention is to provide a new and improved fine diameter endoscope which employs novel image collection optics to enhance image quality.
A further object of the present invention is to provide a new and improved fine diameter endoscope which uses a novel pulsed xenon light source to increase the illumination of the viewing area.
A yet further object of the present invention is to provide a new and improved fine diameter endoscope which may be used as an inexpensive real-time diagnostic tool.